Malic Acid as a Green Catalyst for the N-Boc Protection under Solvent-free Condition

: A protocol for the Chemoselective N-Boc protection of various types of amines has been developed. This includes heteroaryl, aliphatic, and alicyclic amines. The process makes use of malic acid as a catalyst and operates efficiently at ambient temperature without the need for solvents. This technique has been proven to effectively protect a wide range of functionalized amines containing both electron-donating and electron-withdrawing substituents. The benefits of this method include its fast reaction rate, high selectivity, excellent yield, catalyst recyclability, and environmentally friendly conditions. background: A green, efficient, and solvent-free reaction enlarge for Chemoselective N-Boc protection of aromatic, aliphatic, and heterocyclic amine using malic acid-catalyzed under ambient temperature. The described technique successfully performs the N-Boc on a wide range of functionalized aliphatic, aromatic, and hetero-aromatic amines. The advantage of this method has studied the different types of amines that contain electron-donating as well as electron-withdrawing substituents. The reaction works by rapid reaction rate, high selectivity, solvent-free, excellent yield, catalyst recycle, and greener route. This work presents a green, economical, and eco-friendly protocol. result: In the present work to investigate the scope and disadvantages of this solvent-free N-ter-butoxycarbonylation of amine derivatives catalyzed under malic acid, we can study with the model the reaction of aniline react with di-ter-butyl carbonate (1:1 mmol) and malic acid (15 mol%) under solvent-free reaction conditions to give ter-butyl-phenyl carbonate. (Scheme 2) The reaction was completed within 5 min at room temperature and the corresponding N-Boc protected aniline was obtained in 98 % yield. To appreciate the role of malic acid on the N-Boc protection of amine, we have analyzed the reaction of aniline with di-ter-butyl carbonate in catalyst-free conditions at room temperature. It should be noted that the catalyst-free condition and reaction time of 12 h, were obtained in a 25 % yield. Whereas after 24 hours, it was observed to increase only 37 % yield. All amines derivatives undergo reaction at room temperature without a catalyst for 24 h. The N-Boc protection of amine under the malic acid applies to increases yield and reaction time as compared to the absence of a catalyst.